[bess] draft-ietf-bess-rfc7432bis

[Alexander Vainshtein <[e-mail]>]

Hi all,
I have a few questions about the last para of Section 15 of the 7432bis draft<https://datatracker.ietf.org/doc/html/draft-ietf-bess-rfc7432bis-10#section-15> which it says (same as in the original RFC 7432):

If two (or more) PEs advertise the same MAC address with the same sequence number but different Ethernet segment identifiers, a PE that receives these routes selects the route advertised by the PE with the lowest IP address as the best route. If the PE is the originator of the MAC route and it receives the same MAC address with the same sequence number that it generated, it will compare its own IP address with the IP address of the remote PE and will select the lowest IP. If its own route is not the best one, it will withdraw the route.

Now my questions:

  1.  It seems that the situation in which two (or more) PEs advertise the same MAC address with the same sequence number but different Ethernet segment identifiers  can only occur as the result of a race condition between the data plane that locally learns the MAC address in question and the control plane that receives advertisement for this MAC address form other PEs. Is this correct?
  2.  Assuming affirmative answer for the previous question: I can easily see how such race condition can occur in the case of the MAC address in question being locally learned by different PEs at 3 (three) different Ethernet Segments. Do you think it may occur in scenarios with just two different Ethernet Segments?
  3.  It seems that the tie-preaking procedure defined in the quoted text does may result in inconsistency between the data plane and EVPN control plane and consequent traffic loss (because the best route selected in accordance with the tie-breaking procedure does not have to match actual latest location of the MAC address in question).  Is this correct? If yes, did you consider a recommendation to notify the operator in this case?

Your timely feedback will be, as always, highly appreciated.

Regards, and lots of thanks in advance,
Sasha

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